全文获取类型
收费全文 | 1630篇 |
免费 | 16篇 |
国内免费 | 40篇 |
专业分类
安全科学 | 22篇 |
废物处理 | 108篇 |
环保管理 | 154篇 |
综合类 | 141篇 |
基础理论 | 294篇 |
环境理论 | 2篇 |
污染及防治 | 559篇 |
评价与监测 | 297篇 |
社会与环境 | 105篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 59篇 |
2022年 | 172篇 |
2021年 | 114篇 |
2020年 | 25篇 |
2019年 | 47篇 |
2018年 | 82篇 |
2017年 | 89篇 |
2016年 | 110篇 |
2015年 | 44篇 |
2014年 | 80篇 |
2013年 | 177篇 |
2012年 | 74篇 |
2011年 | 92篇 |
2010年 | 68篇 |
2009年 | 59篇 |
2008年 | 73篇 |
2007年 | 54篇 |
2006年 | 64篇 |
2005年 | 36篇 |
2004年 | 24篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1979年 | 2篇 |
1974年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 3篇 |
1962年 | 2篇 |
1961年 | 4篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1956年 | 2篇 |
1955年 | 4篇 |
1953年 | 1篇 |
排序方式: 共有1686条查询结果,搜索用时 15 毫秒
851.
Xinquan Zhang A. Senthil Kumar Mustafizur Rahman Chandra Nath Kui Liu 《Journal of Manufacturing Processes》2012,14(3):378-387
The elliptical vibration cutting (EVC) technique has been found to be a promising technique for ultraprecision machining of various materials. In each overlapping EVC cycle, the thickness of cut (TOC) of work material, and the tool velocity get continuously varied. These two inherent phenomena, in fact, introduce transient characteristics into its cutting mechanics, which are considered to be different from the one applied for conventional cutting technique. Recently, a few theoretical models have been developed to understand the material removal mechanism with the EVC technique; however, in those studies, the transient phenomena were not considered. In the present research, an analytical force model for the orthogonal EVC process was developed in order to fully understand the EVC mechanism, and to more accurately predict the transient cutting force values. Three important factors: (i) transient TOC, (ii) transient shear angle, and (iii) transition characteristic of friction reversal were investigated and analyzed mainly based on geometric modeling and the Lee and Shaffer's slip-line solution. Mathematical evaluation shows that they may have significant influence on EVC process, and thus on its output performance. In order to validate the proposed force model, a series of low-frequency orthogonal EVC tests were conducted. The experimental transient cutting force values were compared with the predicted values calculated using the proposed model, and they are found to be in a good agreement with each other. 相似文献
852.
Subas Chandra Asa Prasanta Rath Unmesh Chandra Panda Pankaj Kumar Parhi Satyanarayan Bramha 《Environmental monitoring and assessment》2013,185(8):6719-6737
In the present study, concentration of some selected trace metals (Fe, Mn, Ni, Co, Pb, Zn, Cu, Cr and Cd) are measured in Brahmani, Baitarani river complex along with Dhamara estuary and its near shore. Chemical partitioning has been made to establish association of metals into different geochemical phases. The exchangeable fraction is having high environmental risk among non-lithogeneous phases due to greater potential for mobility into pore water. The metals with highest bio-availability being Cd, Zn and Cr. The metals like Mn, Zn, Cd and Cu represent an appreciable portion in carbonate phase. Fe–Mn oxides act as efficient scavenger for most of the metals playing a prime role in controlling their fate and transport. Among non-lithogeneous phases apart from reducible, Cr showed a significant enrichment in organic phase. Risk assessment code values indicate that all metals except Fe fall under medium-risk zone. In estuarine zone Cd, Zn, Pb and Cr are released to 32.43, 26.10, 21.81 and 20 %, respectively, indicating their significant bio-availability pose high ecological risk. A quantitative approach has been made through the use of different risk indices like enrichment factor, geo-accumulation index and pollution load index. Factor analysis indicates that in riverine zone, Fe–Mn oxides/hydroxides seem to play an important role in scavenging metals, in estuarine zone, organic precipitation and adsorption to the fine silt and clay particles while in coastal zone, co-precipitation with Fe could be the mechanism for the same. Canonical discriminant function indicates that it is highly successful in discriminating the groups as predicted. 相似文献
853.
854.
855.
Vikas Kumar T. K. Das Dhruba Jyoti Sarkar Shashi Bala Singh Rashmi Dhaka 《Journal of environmental science and health. Part. B》2017,52(6):402-409
Controlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t1/2) ranged between 0.06 and 4.8 days in case of GG-NHG and 4.4 and 12.6 days for the GG-HG formulations. Weed control index (WCI) of GG-HG and GG-NHG formulations was similar to that of the commercial formulation and the herbicidal effect was observed for relatively longer period. Guar gum-based biopolymeric hydrogels in both macro and nano particle size range can serve as potential carriers in developing slow release herbicide formulations. 相似文献
856.
Pankaj Kumar Manish Kumar A. L. Ramanathan Maki Tsujimura 《Environmental geochemistry and health》2010,32(2):129-146
Arsenic contamination in groundwater is of increasing concern because of its high toxicity and widespread occurrence. This
study is an effort to trace the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain of
India through major ion chemistry, arsenic speciation, sediment grain-size analyses, and multivariate statistical techniques.
The study focuses on the distinction between the contributions of natural weathering and anthropogenic inputs of arsenic with
its spatial distribution and seasonal variations in the plain of the state Bihar of India. Thirty-six groundwater and one
sediment core samples were collected in the pre-monsoon and post-monsoon seasons. Various graphical plots and statistical
analysis were carried out using chemical data to enable hydrochemical evaluation of the aquifer system based on the ionic
constituents, water types, hydrochemical facies, and factors controlling groundwater quality. Results suggest that the groundwater
is characterized by slightly alkaline pH with moderate to strong reducing nature. The general trend of various ions was found
to be Ca2+ > Na+ > Mg2+ > K+ > NH4
+; and HCO3
− > Cl− > SO4
2− > NO3
− > PO4
3− > F− in both seasons. Spatial and temporal variations showed a slightly higher arsenic concentration in the pre-monsoon period
(118 μg/L) than in the post-monsoon period (114 μg/L). Results of correlation analyses indicate that arsenic contamination
is strongly associated with high concentrations of Fe, PO4
3−, and NH4
+ but relatively low Mn concentrations. Further, the enrichment of arsenic is more prevalent in the proximity of the Ganges
River, indicating that fluvial input is the main source of arsenic. Grain size analyses of sediment core samples revealed
clay (fine-grained) strata between 4.5 and 7.5 m deep that govern the vertical distribution of arsenic. The weathering of
carbonate and silicate minerals along with surface-groundwater interactions, ion exchange, and anthropogenic activities seem
to be the processes governing groundwater contamination, including with arsenic. Although the percentage of wells exceeding
the permissible limit (50 μg/L) was less (47%) than that reported in Bangladesh and West Bengal, the percentage contribution
of toxic As(III) to total arsenic concentration is quite high (66%). This study is vital considering that groundwater is the
exclusive source of drinking water in the region and not only makes situation alarming but also calls for immediate attention. 相似文献
857.
The promise of Beijing: Evaluating the impact of the 2008 Olympic Games on air quality 总被引:1,自引:0,他引:1
Yuyu Chen Ginger Zhe Jin Naresh Kumar Guang Shi 《Journal of Environmental Economics and Management》2013
To prepare for the 2008 Olympic Games, China adopted a number of radical measures to improve air quality. Using the officially reported air pollution index (API) from 2000 to 2009, we show that these measures improved the API of Beijing during and a little after the Games, but a significant proportion of the effect faded away by October 2009. For comparison, we also analyze an objective and indirect measure of air quality at a high spatial resolution – aerosol optimal depth (AOD), derived using the data from NASA satellites. The AOD analysis confirms the real but temporary improvement in air quality, it also shows a significant correlation between air quality improvement and the timing and location of plant closure and traffic control. These results suggest that it is possible to achieve real environmental improvement via stringent policy interventions, but for how long the effects of these interventions will last will largely depend on the continuation of the interventions. 相似文献
858.
The metabolic fate of mancozeb in tomato (Lycopersicon esculentum Mill.) fruits was evaluated. Results indicate rapid dissipation of mancozeb and its metabolic conversion to ethylenethiourea (ETU), the carcinogenic metabolite. Treatment with mancozeb at flowering stage resulted translocation of ETU in newly emerged fruits indicating the systemic nature of ETU. ETU was detected within one hour of final spraying of mancozeb at the doses of 1.5 and 3?kg a.i./ha. The residue level of ETU increased up to 3-day for both the treatments, which then rapidly dissipated to safer metabolite ethyleneurea (EU) and reached the below detectable limit within 25 days. Cooking of fresh tomatoes caused decontamination of mancozeb residues, which was associated with simultaneous increase in ETU residues. The degradation pattern of ETU after application of mancozeb was slower as compared to the spraying of ETU as such on the crop. A pre-harvest interval of 25 days is recommended. 相似文献
859.
Mohammad Fareed Chandrasekharan Nair Kesavachandran Manoj Kumar Pathak Vipin Bihari Mohammed Kuddus 《毒物与环境化学》2013,95(8):1601-1609
In this study, risk assessment for visual disturbances among farm workers spraying agricultural pesticides in farms have been assessed. A cross-sectional study for the assessment of visual disturbances was undertaken using questionnaire survey and clinical examination among agricultural workers exposed to pesticides. Two hundred and thirty nine pesticide sprayers participated in the study. The study was compared to 110 controls not occupationally exposed to pesticides with similar socio-economic status. The prevalence of ocular morbidity was found to be 40% among pesticide sprayers which was significantly higher (p?0.01) as compared to controls. The symptoms among morbid subjects were found to be blurred vision, lacrimation, pain in eyes, red swollen eyes, and irritation of eyes. Exposure wise assessment of ocular symptoms among pesticide sprayers illustrates that exposure time elevates the ocular problems among sprayers. The cholinesterase activity was found to be significantly depleted (p?0.01) among pesticide sprayers as compared to controls which show the exposure of organophosphate pesticides among them. The visual disturbances observed among pesticide sprayers clearly exhibit that eyes get exposed by pesticides during spraying operations in agriculture and eventually get affected leading to ocular illness. 相似文献
860.
Ozonolysis combined with photocatalysis was used as a new approach for the treatment of textile dye wastewater containing azo dyes. The color reduction was very fast when only ozone was used for the treatment, but a 90% Total Organic Carbon (TOC) reduction was obtained only during a combined treatment. Reactive Black 5 dye containing two different percentages of NaCl was used for the experiment. The color reduction was fast in the neutral and basic pH. However for a fast TOC reduction acidic pH was found to be more effective. On‐line UV‐Vis spectrophotometry was used to measure the color reduction. 相似文献